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Accuphase C-3850 Preamplifier and P-7300 Power Amplifier

The Accuphase brand was originally marketed under the company name of Kensonic Laboratory, Inc. in 1972. To celebrate its tenth anniversary, the company changed its name to Accuphase Laboratory, Inc. The name Accuphase was chosen as a merging of the words accurate and phase. One of the basic ideologies of the company has been quality over quantity, from the first C-200 preamplifier and P-300 amplifier to the latest products under evaluation—the C-3850 preamplifier ($43,500) and P-7300 power amplifier ($32,000).

First introduced in the U.S. at CES 2015, the C-3850 preamplifier is the company’s newest flagship model, replacing the C-3800 (introduced in July of 2010). Accuphase says the C-3850 exemplifies the knowledge gained over the nearly 45 years of the company’s existence in product construction, circuit design, component selection, and technology, yielding “an audio instrument that admits no compromise in the pursuit of peerless performance.” While I can’t confirm that statement for every reader, I believe that Accuphase takes a fundamentally sound design approach with methods and practices that are on a level with today’s best manufacturing, engineering, and quality-assurance processes.

One of the primary functions of a preamplifier is volume control. The C-3850 accomplishes this using what the company calls an Accuphase Analog Vari-gain Amplifier (AAVA). AAVA takes the input voltage of the music signal and converts it into weighted current using 16 types of voltage-to-current (V-I) amplifiers. Each of the 16 weighted current output stages are turned on and off by individual current switches. These V-I current stages are summed to form a variable gain circuit that adjusts the volume of the input music signal, yielding 65,536 (216) individual current levels. Before the music signal is transferred through the next stage of the preamplifier, the signal is converted back to a voltage using a current-to-voltage (I-V) amplifier. With this level (no pun intended) of refinement, the microprocessor that controls the input-signal current level is able to maintain proper channel balance throughout the operating range, to precisely set signal level, to adjust and maintain L-R balance, and to control the signal attenuator button without adding more circuitry to the signal path.

Accuphase feels this AAVA approach to volume control removes the effects of impedance changes, frequency response inconsistencies, and large variances in signal-to-noise ratios when listening at low levels. The C-3850 evolves the AAVA principle by using dual AAVA (balanced AAVA) circuits in parallel to achieve the same performance when using balanced input to balanced output signals.

Internally, the C-3850 is a dual-mono design with individual power supplies (including toroid transformers) with 60,000 microfarads of capacitance per channel. Each channel (left and right) has nine unit-amplifier printed-circuit board (PCB) cards per side that are made from glass-cloth fluorocarbon resin with gold-plated copper-foil surfaces. The channels are separated by 8mm of hard aluminum that is said to increase rigidity and reduce vibration. A main PCB serves as the motherboard that ties the 18 unit amplifier cards, the power supply circuit cards, the front panel PCB and display, and rear-panel input and output interfaces together.

Externally, the C-3850 follows the Accuphase tradition of refined visual appeal with its golden-hue metal front panel and high-gloss natural-wood-grain cabinet—with vented grilles on top to dissipate heat generated by the internal circuitry and unit amplifier cards. Scanning the front panel from left to right one sees the input selector knob with power button directly below; the subpanel cover with the display panel above it; a subpanel access button; a headphone jack; and the volume knob with attenuator button below it.

 

Accuphase put a lot of thought into the volume knob, which is connected to a sensor that sends position information to the microprocessor for proper volume adjustment. Accuphase says the volume knob is extruded from a solid aluminum block and mounted to a large diameter shaft. This is said to provide the right amount of inertia when combined with the low-friction internal mechanism, and to ensure smooth feel and quiet motor operation (when using the remote control). The operation of the volume knob during evaluation seemed to confirm the stated goals of the manufacturer.

The display panel shows a digital readout of the selected input and volume level. Additionally, there are indicators for output (inv, off, and external pre), recorder (on and play), attenuation (-20dB), and the loudness-compensation network (a three-position loudness compensator that boosts low-end presence). Pressing the button for the subpanel opens the drawer and reveals button controls for display, phase (phase inversion can be set individually for each channel), mono, and recorder. Rotary switches for output (ext. pre, all, bal, line, off), gain (12dB, 18dB, 24dB), balance (+/– 4dB L-R), compensator (off, 1, 2, 3), and ’phones level (low, med, high) are also accessible. The rear panel features four balanced XLR inputs, six single-ended inputs, two sets of balanced XLR outputs, two sets of single-ended outputs, one set of recorder playback-and-recording single-ended inputs and outputs, a set of external preamplifier inputs (single-ended and balanced), and the AC power supply IEC connector.

The supplied remote control (RC-210) has buttons for input selection (direct or toggle), volume adjustment, and attenuator on/off. There are five additional buttons for CD/SACD player control (stop, play, pause, back, and next) that will operate Accuphase disc players.


Setting up the C-3850 is relatively straightforward. In addition to making the usual connections for input source components and output, the user has options for a few additional settings. The loudness compensator can be engaged at various levels if the user needs/desires more low-frequency presence. (In this evaluation the compensator feature was tested for functionality but not used during normal listening sessions.) Depending on the output cable configuration, the output control can be set for an external preamp (e.g. home-theater bypass—not tested), balanced, single-ended, or balanced and single-ended. The volume level display can be adjusted to work in attenuation mode (default) or gain mode; both modes were used in this evaluation. The C-3850 is set for pin-3 “hot” on the XLR input and output. Depending on the input source and the amplifier connected to the output, the individual input phase inverter can be activated to adjust for any condition. If the user gets confused, the instruction manual has a usage table to help set the phase (inverted or non-inverted) for all of the connections. The gain setting can be set for 12dB, 18dB, or 24dB. In every configuration in which the C-3850 was used, the preferred gain setting was 24dB, which yielded more dynamic and rhythmic drive on all types of music.

The P-7300 stereo power amplifier is rated at 125Wpc into 8 ohms, 250Wpc into 4 ohms, 500Wpc into 2 ohms, and a stable 800Wpc (music signal) into 1 ohm. Maximum output power in normal operating mode is listed as 220Wpc, 383Wpc, 620Wpc, and 899Wpc respectively. The P-7300 replaces the P-7100 introduced in 2006. Like the C-3850, the P-7300 improves on the older design, utilizing the same advancements and experience Accuphase has gained over the years. The P-7300 boasts improved signal-to-noise ratio and a higher damping factor than the P-7100 it replaces.

Internally, the P-7300 contains a large newly developed toroid transformer in the power supply with a total of 112,000 microfarads of filter capacitance. The input stage is a low-noise instrumentation-amplifier topology designed with discrete components in a balanced configuration. Further improvements in the Multiple Circuit Summing (MCS+), which uses multiple circuits paralleled in the same configuration to reduce noise and improve performance, have been extended to the Class A drive stage of the I-V converter. The output stage uses 10 parallel push-pull (20 total) bipolar output transistors per channel. These transistors are directly mounted to the large die-cast aluminum heatsinks on either side of the amplifier that dissipate heat generated by the circuits. A current feedback circuit is utilized to achieve negative feedback in an effort to keep the feedback circuit impedance low and phase shift at a minimum.

The outside of the P-7300 has a golden-hue metal front panel with the die-cast aluminum heatsinks integrated into the chassis to form the side panels. On the rear of the amplifier are two sets of speaker terminal binding posts (for bi-wiring) for both left and right channel outputs, single-ended (and balanced) inputs for each channel, a balanced input phase selector switch, and an IEC AC power supply. Additionally, there is a rotary selector switch for the amplifier configuration: normal mode for stereo operation, dual mono mode for bi-amping, and bridge mode for monoblock operation (500Wpc into 8 ohm, 1000Wpc into 4 ohm). On the front panel, the amplifier has a 4-stage gain-selector rotary switch that has a max setting (28dB of gain) with additional adjustable settings of –3dB, –6dB, and –12dB (relative to the max setting). Next to the gain-selector switch is an input-selector button (single-ended or balanced), a main power button, and a power-meter-control rotary switch. The power-meter-control selections are off, normal, 3 SEC (peak hold for 3 seconds), and infinite (infinite peak hold). The center of the front panel houses the power meters for both channels. Above the left power meter are hold indicators for the power-meter-control settings (3 seconds or infinite), while function indicators (bridge mode, dual mono, single-ended, and balanced) are above the right power meter.

 

In setting up the P-7300, the speaker outputs were used in a bi-wired (and single-wired) configuration with balanced XLR inputs. The phase selector switch was set according to the preamplifier used at the time. The majority of the time it was set to the default (pin-3 “hot”) for use with the C-3850 and pin-2 “hot” when used with the Placette Audio Active preamplifiers. The power meters were set to normal mode for most daily operation. Listening tests favored the –3dB or –6dB setting for the gain-selector switch. The max setting tended to add a bit of edge to the sound while the –12dB setting tended to sound a bit less dynamically robust. The speakers used during the evaluation were Vandersteen Model 3A Signature and the Magnepan 20.7. Occasionally, a pair of Vandersteen 2Wq subwoofers were employed to add additional bottom-octave drive to fill my rather large 18′ wide and 43′ deep and 8′ high listening space. The P-7300 was able to control and drive any of the above speakers without sounding as if it were having any difficulties. The level of bass control the amplifier had on the 20.7 (as well as on the 3A Signature) was as good as any other amplifier I’ve used with these speakers.

When combined, the C-3850 and P-7300 become the heart of a soulfully solid, bottom-up sounding reproduction system. The solidity of the presentation from multiple sources (music and source equipment) appeared to be palpable in all cases. One of my first observations was the more forceful drive and vigor the Accuphase pair presented. Chris Isaak’s “Kings of the Highway” from the Heart Shaped World LP had the characteristically saturated soundstage it always has but with more expansion of the soundstage in all directions. Additionally, the added presence in the bass and lower midrange gave the music perceptively more powerful drive. This same characteristic was noticed on Mighty Sam McClain’s “Too Proud” from the Give It Up to Love LP with the bass and drums commanding attention when called for. On “So Far Away” from Mobile Fidelity’s reissue of Dire Straits’ Brothers in Arms LP, the Accuphase gear further solidified the foundation, maintaining low-octave energy throughout. The track seemed rooted to the bass drum, with no noticeable overhang, and the bass guitar.

Another plus was the way string instruments and organs were presented with clarity while not being pushed forward in the musical mix. Guitar separation and multitrack layering of the instruments on “Kings of the Highway” and “So Far Away” were easy to observe, and all instruments had an additional amount of weight and presence. The Hammond B-3 played by Bruce Katz on “Too Proud” filled the soundstage with this instrument’s captivating sound and made it a primary underpinning ingredient, setting the mood for the performance.


On vocals, there appeared to be a shift toward presenting more power through the chest of the singer rather than a thinner head tone. On all of the songs mentioned above, the vocals were in natural proportion and easily enjoyable. The Speaker’s Corner reissue of the Decca recording of Ravel’s Scheherazade conducted by Ernest Ansermet featuring French soprano Régine Crespin produced exceptional sound through the C-3850/P-7300 combo. Crespin’s voice was very powerful yet sweet and smooth all the way through her dynamically impressive fortissimos. The playback through this Accuphase combination had the most strikingly solid vocal foundation I’ve heard from this LP. Crespin’s voice filled the performance venue the way one observes during a live performance, with an additional amount of fullness that was captivating. The accompanying orchestral performance was just as convincing, with similar characteristics. Instrument placement was where one would expect with a proper representation of a performance venue.

The Accuphase C-3850 and P-7300 operated flawlessly during the evaluation period. In its website literature, it seems Accuphase prioritizes quality over quantity. One example is the use of vibration testing during the manufacturing process on every component. Accuphase’s belief that a single failure for the customer is a 100% failure rate drives its desire for bullet-proof product reliability. I’ve heard four Accuphase products in my listening space and all of them have performed without issue.

The Accuphase combination delivers the distinctive cues that reveal the individuality of the music (or source component) being played. During multiple listening sessions, the C-3850/P-7300 never ventured into the bright and fatiguing—nor did it veer into the soft and dull. The presentation tended to stay close to the sonic lane that provides long-term listening satisfaction with enough resolution, warmth, and soul to allow full exploration of the music being presented. With this setup, the user can tilt to the left brain or right brain depending on mood and desire. An audition is recommended.

Specs & Pricing

Preamplifier
Type: Solid-state
Analog inputs: Four pairs of balanced XLR and six pairs of single-ended RCA
Dimensions: 18-3/4″ x 6-1/8″ x 16-1/48″
Weight: 55.1 lbs. net
Price: $43,500

Power amplifier
Type: Solid-state
Output power: 125Wpc into 8 ohms, 250Wpc into 4 ohms, 500Wpc into 2 ohms
Inputs: Two balanced XLR and two single-ended RCA
Outputs: Two pairs of speaker terminal binding posts per channel
Dimensions: 18-5/16″ x 9-3/8″ x 20-9/32″
Weight: 107.2 lbs. net
Price: $32,000

ACCUPHASE LABORATORY, INC.
2-14-10 Shin-ishikawa, Aoba-ku,
Yokohama City, Kanagawa Prefecture, 225-8508 Japan
accuphase.com

AXISS AUDIO (U.S. Distributor)
17800 South Main Street, Suite 109
Gardena, CA 90248
(310) 329-0187
axissaudio.com

By Andre Jennings

My professional career has spanned 30+ years in electronics engineering. Some of the interesting products I’ve been involved with include Cellular Digital Packet Data modems, automotive ignition-interlock systems, military force protection/communications systems, and thrust-vector controls for space launch vehicles.

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